That Spaniard's name was Hernán Cortés. In 1519 he set foot in Mexico and would start the conquest of the country. One must be either brave or stupid to do something like that, because at the time he and his soldiers arrived in Tenochtitlán, the city already had 200.000 inhabitants. However, due to good fortune and Cortés' intelligence, they succeeded in their attempt and in 1521 Mexico no longer pertained to the Aztecs, but to the Spanish Crown. Cortés decided to rebuild the city he had just destroyed but would call it "Mexico", the name the Aztecs used to refer to themselves. Maybe to honour them... but most of all because he was not able to pronounce Tenochtitlán, and who could blame him?
By 1700 the city's population had grown to about a hundred thousand people: whites, indians, slaves imported from Africa and all kinds of mixtures of those races. The elite was formed by the gachupines or Spanish immigrants and the criollos or Spanish people born in the New World. At the beginning of the 18th Century the German scientist and explorer Alexander von Humboldt described Mexico City as one of the most prospering cities of the New World. Meanwhile, Spain was involved in many European wars and had neither time nor money to invest in the colony. That and the independence of the United States in 1776 were the main causes of the inevitable: in 1821 Mexico became an independent country.